Abstract

We present the design and construction of a diagnostic system of the plasma parameters by means of electrical probes. The novelties of the system are the protection provided to the electrical probe with a guard, thus minimizing the probe deterioration, and the automatic positioning device associated with the probe. This system consists of: the electronic instrumentation for the electrical probe bias; two control systems, one for the guard’s motion, and another for the positioning of the electrical probe; and finally, a data acquisition system. During the system’s operation, and based on the data measured by the electrical probe at different positions where the data acquisition is carried out, the following parameters are available in real time: floating voltage, ion saturation voltage and current, electron temperature, and plasma’s voltage and density. The motion of the guard and electrical probe array is programmable up to a maximum speed of 1 cm/s, and the time required for the bias of the probe, the measuring and storing of the signal, and the generation of an ASCII data file is approximately 10 ms. With this system, the duty cycle of the probe is extended due to the shielding provided by the guard. Likewise, the reduction of deposits of spurious materials on the probe results in a more reliable measuring process of the plasma parameters.